The $P-V$ diagram for an ideal gas in a piston cylinder assembly undergoing a thermodynamic process is shown in the figure. The process is

In thermodynamics, an isobaric process is a type of thermodynamic process in which the pressure of the system stays constant: $\Delta P=0$. The heat transferred to the system does work but also changes the internal energy of the system. $P=$constant $\Rightarrow$Isobaric process.